1. Field of the Invention
This invention relates generally to a sheet feeding method and apparatus, and more particularly to means for closing selected ports of a vacuum sheet feed apparatus.
2. Description of the Prior Art
In modern reproduction equipment such as printing presses or copier/duplicators, copies are generally made on discrete copy sheets. The sheets are fed seriatim, either mechanically or pneumatically, from a supply along a transport path to a printing station where an ink or toner image is placed on the sheets. One type of pneumatic feeder which has been adapted for use in such reproduction equipment is a rotating vacuum feeder as shown in U.S. Pat. No. 2,770,458 issued Aug. 14, 1953, in the name of Halahan, et al. Such a vacuum feeder has a series of ports in the wall of a rotating tubular housing, the ports being spaced in axial alignment along the housing transverse to the sheet travel path. A vacuum source connected to the interior of the housing creates a sub-atmospheric pressure condition in the area of the ports. The housing is rotated to locate the ports adjacent to a supply stack of discrete sheets where the vacuum causes the portion of a sheet opposite the ports to be stripped from the stack and tacked to the housing. As the housing is rotated from this position, the tacked sheet is drawn from the stack and fed along the transport path. While such an arrangement is generally satisfactory for efficient feeding of discrete sheets, misfeeds or objectional multiple sheet feeds may occur if the sheets have holes which are aligned with the ports in the housing during transport. Sheets upon which it is often desired to make copies include, for example, 3-hole and 7-hole punched paper.